1. Field of the Invention
The present invention pertains to the field of assisted visual perception. Specifically, the present invention provides for a filter, such as a notch filter, that orthogonalizes signals detecting blood oxygen concentration and blood volume through a skin of a human.
2. The Relevant Technology
Color changes in human skin are widely believed to signal emotions such as anger, arousal, fear, and fatigue in humans and all other higher primates. Other similar color changes are indicative of various medical conditions such as hypoxia, cyanosis, jaundice, and also various vasospastic disorders. Recent evidence suggests that the human eye is specially tuned to detect subtle changes in skin color that correspond to changes in blood volume (e.g., signaling anger or some other altered emotional state) and oxygenation of hemoglobin (e.g., signaling jaundice or some other illness). While these changes in color are visible to the unassisted eye, perception of them is in fact severely damped due to a particular range of the visible light spectrum in which the reflectance spectrums of changes in blood volume and oxygenation of hemoglobin is erratic.